Slim object detection using multi-polarized millimeter wave signals

ABSTRACT

A millimeter or mm-wave system includes transmission of a millimeter wave (mm-wave) radar signal by a transmitter to an object. The transmitted mm-wave radar signal may include at least two signal orientations, and in response to each signal orientation, the object reflects corresponding signal reflections. The signal reflections are detected and a determination is made as to location of the object.

RELATED APPLICATIONS

This application claims the benefit of priority of U.S. ProvisionalPatent Application Ser. No. 62/456,479 filed Feb. 8, 2017, incorporatedherein by reference.

BACKGROUND

Radar systems have been used by commercial, private, and militarysectors to detect presence and track locations of relatively large, fastmoving targets. For example, the radar systems have been used to tracktargets such as rockets, people, automobiles, aircraft, etc. However,detecting of very small and slow moving targets at short distances, andin the presence of high background clutter or noise, has not been a highpriority. There have been a number of attempts to design a radar systemto detect the small and slow moving targets and these attempts have beenunreliable for number of reasons.

First, a use of a pulse radar to detect and track small and slow movingtargets have been limited by radar cross section of the target, which isvery small, and any background noise may tend to blind the radar. Thepulse radar has a minimum range, and the limited radar cross section ofthe target may further limit the detection and tracking of the target.Secondly, use of a Continuous Wave (CW) Doppler Radar is efficient for aparticular configuration of the target; however, the CW Doppler Radar islimited by surrounding noise when detecting small and fast movingobjects.

Synthetic Aperture Radar (SAR) uses multiple polarization antennas. SARsystems typically may be used satellite or large scale aircraft. SARsystems rely on accurately known/determined motion information, whichmay be provided by a sensor of an antenna carrier to achieve high imageresolution. The information from co- and cross-polarization is combinedfor object classification. It is desirable to provide for a standalonesystem without use of a separate sensor to provide information regardingco- and cross-polarization. SAR systems further require a specificprocessing of polarization channels. The higher SNR channel between twodifferent polarization channels is used for object detection andlocalization.

SUMMARY

Described herein is a technology for a millimeter or mm-wave detectionand particularly, a mm-wave system for detecting slim, fine, and smallobjects during a dense weather condition and noisy environment. Themm-wave system, for example, may include a plurality of transmitters fortransmission of a mm-wave radar signal to an object. The transmittedmm-wave radar signal may include at least two signal orientations suchas at least one horizontally polarized signal, and at least onevertically polarized signal, which may be transmitted by differenttransmitters with corresponding different pre-configured fixedpolarizations. In response to each signal orientation, the object mayreflect signals that correspond to each of the at least two signalorientations. Based on the reflected signals, a processor may determinethe signal orientation that may include a highest signal to noise ratio(SNR), higher signal magnitude, and the like, and utilize the determinedsignal orientation to detect and determine location of the object.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description is described with reference to accompanyingfigures. In the figures, the left-most digit(s) of a reference numberidentifies the figure in which the reference number first appears. Thesame numbers are used throughout the drawings to reference like featuresand components.

FIG. 1 is an example scenario illustrating an example application of amillimeter-wave (mm-wave) system as described herein.

FIG. 2 illustrates an example mm-wave system as described in presentimplementations herein.

FIG. 3 illustrates an example detection of an object by a mm-wave systemas described in present implementations herein.

FIG. 4 illustrates an example use of multi-polarization signals by amm-wave system as described in present implementations herein.

FIG. 5 is an example process chart illustrating an example method fordetecting slim objects by a mm-wave system as described herein.

DETAILED DESCRIPTION

FIG. 1 is an example scenario 100 illustrating an example application ofa mm-wave system as described herein. As shown, the scenario 100includes, for example, a device 102 with a mm-wave system 104, a firstobject 106, a second object 108, transmitted mm-wave radar signals 112,and reflected return—mm-wave radar signals 114.

The device 102, for example, may be remotely controlled and includesremote-controlled sensors and camera systems such as the mm-wave system104, digital cameras, etc. Although the remote controlled device 102,for example, may use the installed digital cameras to perform a threedimensional (3D) survey of a particular area during an operation, theinstalled digital cameras may be limited by size and dimensions of theobjects (i.e., first object 106 and/or second object 108) to be detectedand by surrounding weather conditions. In this example, the device 102may be a bomb disposal robot, a drone, an automobile, a toy, or amachine that may require detection of miniature or thin objects asfurther described below.

As opposed to digital cameras, the mm-wave system 104 may be configured,for example, to transmit W band (75-110 GHz) mm-wave radar signals todetect and determine locations of small and thin first object 106 and/orsecond object 108 on a dense weather conditions and in a noisyenvironment. The small and thin objects may include electrical wires,metallic cables, thin plastic wires, skinny rubber cables, fine meshwires, and the like. In this example, the mm-wave system 104 may operateat the W band (75-110 GHz) and particularly, at 76-81 GHz range intransmitting the mm-wave radar signals using different combinations oftransmission polarizations i.e., horizontal and/or verticalpolarizations. In this example still, the mm-wave system 104 may use thesame channel for transmission and receiving of mm-wave radar signals.

The mm-wave system 104 transmits, for example, the W band—mm-wave radarsignals 112-2 to the direction of the first object 106. In response tothis transmission, the mm-wave system 104 may receive return—mm-waveradar signals 114-2 from the first object 106 using the sametransmission channel. In this example, the transmitted mm-wave radarsignals 112-2 may have at least two signal orientations such as onehorizontal signal polarization and one vertical signal polarization thatmay be transmitted by different transmitters with differentpre-configured fixed polarizations. In this case, the receivedreturn—mm-wave radar signals 114-2 may include signal reflections thatcorrespond to each signal orientation of the transmitted mm-wave radarsignals 112.

Similarly, the mm-wave system 104 transmits, for example, thetransmitted mm-wave radar signals 112-4 to the direction of the secondobject 108 and in response to this transmission, the mm-wave system 104may receive the return—mm-wave radar signals 114-4 from the secondobject 108.

In the examples above, the mm-wave system 104 may be configured to usethe received return - mm-wave radar signals 114-2 and 114-4 in order todetect presence of the first object 106 and the second object 108,respectively. Furthermore, the mm-wave system 104 may be configured todetermine and utilize the signal orientation that may facilitateefficient identification of the location and distance of the firstobject 106 and/or second object 108 from the device 102. For example,the mm-wave system 104 may include receivers with differentpre-configured fixed polarizations. In this example, each receiver witha particular pre-configured fixed polarization may receive thereturn—mm-wave radar signals 114 based on the signal orientation of thesource—mm-wave radar signals 112. In this example still, the mm-wavesystem 104 may use the signal orientation with highest signal to noise(SNR) ratio in identifying the location and distance of the first object106 and/or second object 108 from the device 102.

Although the example basic block diagram of the device 102 illustratesin a limited manner the basic components, other components such asprocessors, storage, applications, memory, etc. were not described inorder to simplify the embodiments described herein

FIG. 2 illustrates an example mm-wave system 104 as described in presentimplementations herein. As shown, the example mm-wave system 104 mayinclude a plurality of transmitters 200, a plurality of receivers 202, apolarization controller 204, and a signal processor 206. Furthermore,FIG. 2 shows a horizontally polarized mm-wave radar signal 208 and avertically polarized mm-wave radar signal 210 that may be transmitted bya first transmitter 200-2 and a second transmitter 200-4, respectively.Furthermore, FIG. 2 shows a horizontal polarization reflection signal212 and a vertical polarization reflection signal 214 that correspond tothe transmitted horizontally polarized mm-wave radar signal 208 and thevertically polarized mm-wave radar signal 210, respectively. Thehorizontal polarization reflection signal 212 and the verticalpolarization reflection signal 214 may be received by a first receiver202-2 and a second receiver 202-4, respectively, of the plurality ofreceivers 202.

Each transmitter and receiver of the plurality of transmitters andreceivers, respectively, in FIG. 2 may be pre-configured, for example,to have a fixed polarization. For example, the first transmitter 200-2and the second transmitter 200-4 may be pre-configured to havehorizontal and vertical polarizations, respectively. Similarly, thefirst receiver 202-2 and the second receiver 202-4 may be pre-configuredto have horizontal and vertical polarizations, respectively. In thisexample, the first receiver 202-2 and the second receiver 202-4 may beconfigured to receive the transmitted mm-wave signals from the firsttransmitter 200-2 and the second transmitter 200-4, respectively.

As described herein, the plurality of transmitters 200 may be configuredto operate at 76-81 GHz spectrum in transmitting the horizontallypolarized mm-wave radar signal 208 and the vertically polarized mm-waveradar signal 210 using at least two different transmitters withpre-configured fixed polarizations. The at least two differenttransmitters, for example, may be coupled to corresponding transmitterantenna (not shown). Furthermore, although the plurality of transmitters200 in FIG. 2 shows a couple of different transmitters in transmittingthe mm-wave radar signals using at least two different signalorientations i.e., horizontal and vertical polarizations, additionalnumber of transmitters with pre-configured fixed polarizations may beadded and utilized without affecting the implementations describedherein.

The horizontally polarized signals 208 may include antenna electricfields that are parallel to Earth's surface while the verticallypolarized signals 210 may include antenna electric fields that areperpendicular to the Earth's surface. The horizontally polarized signals208 may be transmitted by the first transmitter 200-2, while thevertically polarized signals 210 may be transmitted by the secondtransmitter 200-4.

The transmitted horizontally polarized mm-wave radar signal 208 and thevertically polarized mm-wave radar signal 210 may be received andreflected by the first object 106 as horizontal polarization reflectionsignal 212 and vertical polarization reflection signal 214,respectively. For example, a thin barbed wire—first object 106 mayreceive the horizontally polarized signals 208 of the mm-wave radarsignals 112-2 form the first transmitter 200-2. In this example, thethin barbed wire—first object 106 may reflect the horizontalpolarization reflection signal 212 in response to the receivedhorizontally polarized signals 208 of the mm-wave radar signals 112-2.

Similarly, the thin barbed wire—first object 106, for example, mayreceive the vertically polarized signals 210 of the mm-wave radarsignals 112-2 from the second transmitter 200-4. In this example, thethin barbed wire—first object 106 may reflect the vertical polarizationreflection signal 214 in response to the received vertically polarizedsignals 210 of the mm-wave radar signals 112-2.

In an implementation, and in an example configuration where the thinbarbed wire—first object 106 is positioned orthogonally with thevertically polarized signals 210 from the second transmitter 200-4, thevertical polarization reflection signal 214 may have a lower signal tonoise ratio (SNR) and lower reflected signal magnitudes as compared tothe horizontal polarization reflection signal 212. That is, thehorizontal polarization reflection signal 212 may provide a bettersignal reflection (i.e., higher SNR) for determining presence, location,and distance of the thin barbed wire—first object 106 as compared thevertical polarization reflection signal 214.

The plurality of receivers 202 may include the first receiver 202-2 andthe second receiver 202-4 in receiving the horizontal polarizationreflection signal 212 and the vertical polarization reflection signal214, respectively. The at least two receivers may be coupled tocorresponding receiver antenna (not shown). Furthermore still, althoughthe plurality of receivers 202 in FIG. 2 shows a couple of differentreceivers in receiving the return—mm-wave radar signals using at leasttwo different signal orientations i.e., horizontal and verticalpolarizations, additional number of receivers with pre-configured fixedpolarizations may be added and utilized without affecting theimplementations described herein.

The polarization controller 204 may be coupled to the plurality oftransmitters 200 and the plurality of receivers 202. For example, thepolarization controller 204 may be configured to choose the transmitter(i.e., first transmitter 200-2 or second transmitter 200-4) from theplurality of transmitters 200 to use for the signal transmission, andthe receiver (i.e., first receiver 202-2 or second receiver 202-4) fromthe plurality of receivers 202 for the signal reception. In thisexample, the chosen signal polarization of the receiver at the receiverside may correspond to the signal polarization of the transmitter at thetransmitting side.

In an implementation, the plurality of transmitters 200 may include thetransmitter antennas that convert mm-wave RF electric current intoelectromagnetic waves, which are radiated into space. In thisimplementation, the polarization controller 204 may be configured tochoose the transmitter with a particular signal polarizationconfiguration for transmitting the mm-wave RF electric current intospace. Similarly, during reception, the polarization controller 204 maybe configured to choose the receiver with a particular signalpolarization configuration for receiving the reflected signal. Eachtransmitter and receiver of the plurality of transmitters and receivers,respectively, for example, may include a switch that may be controlledby the polarization controller 204.

The polarization controller 204 may further facilitate differentsequence-combinations of the signal polarizations of the mm-wave radarsignals 112-2. For example, the polarization controller 204 may switchin sequence the first transmitter 200-2 and the second transmitter 200-4to initially transmit the mm-wave radar signals 112-2 in an alternatinghorizontal and vertical signal polarizations fashion. Thereafter, thepolarization controller 204 may utilize the horizontal or the verticalsignal polarization based upon their corresponding SNR as seen at thereceiver side. In this example, the signal polarization with the betterSNR, magnitude, and the like, may be utilized to determine the distanceand location of the first object 106.

The signal processor 206 may be configured to process the receivedhorizontal polarization reflection signal 212 and the verticalpolarization reflection signal 214. For example, the signal processor206 may determine which reflected signal between the horizontalpolarization reflection signal 212 and the vertical polarizationreflection signal 214 may include a higher SNR. In this example, thesignal polarization with the higher SNR (i.e., horizontal polarizationreflection signal 212 or the vertical polarization reflection signal214) may be utilized by the signal processor 206 to determine thedistance and location of the first object 106. In this example still,the signal processor 206 may send control signals that may be receivedby the polarization controller 204 in order to change the alternatingsignal polarization or orientation into a single signal orientation.

For example, as shown in FIG. 2, the barbed wire—first object 106 mayreflect the horizontal polarization reflection signal 212 and thevertical polarization reflection signal 214, which correspond to thehorizontally polarized signals 208 and vertically polarized signals 210,respectively. In this example, the horizontal polarization reflectionsignal 212 may include a signal that produces a higher signal peak valueor higher signal magnitude and a higher SNR as compared to the verticalpolarization reflection signal 214 on a particular sampling rate. Assuch, the signal processor 206 may use the horizontal polarizationreflection signal 212 in the determination of the location of the firstobject 106.

As described herein, the signal processor 206, for example, may utilizea pre-defined SNR-threshold in determining the reflected signal that maybe used to determine location and distance of the first object 106. Thepre-defined SNR-threshold may include a SNR value that may be used todifferentiate between reflected signals of different signalorientations. For example, the signal processor 106 may compare thehorizontal polarization reflection signal 212 and the verticalpolarization reflection signal 214 to the SNR pre-defined SNR threshold.In this example, the signal processor 106 may reject or accept thesignal reflection to be used for determining the presence and distanceof the reflecting object such as the first object 106.

FIG. 3 illustrates an example detection of an object by a mm-wave systemas described in present implementations herein. Particularly, FIG. 3shows the mm-wave system 104 that may be configured, for example, toperform an initial detection of the second object 108, which may includea fine mesh wire that is hard to detect especially at dense weatherconditions. In this example, the transmitted mm-wave radar signal 112-4may include a circularly polarized signal 300 that may be received andreflected by the second object 108. The circularly polarized signal 300,for example, may be generated by activating the first transmitter 200-2and the second transmitter 200-4 that are pre-configured to be out ofphase by 90° from each other. In another example, one of the transmitterof the plurality of transmitters 200 may be pre-configured to have afixed circular polarization.

As shown, the transmitted circularly polarized signal 300 may bereceived by the second object 108 and thereafter reflected as signals302, which may include intermittent peak signals 304 on a particularsignal orientation of the circularly polarized mm-wave radar signal112-4. For example, the return—mm-wave radar signal 114-4 which isrepresented by the signals 302 may include the peak signals 304 that mayoccur at about 45 degrees of every cycle. In this example, the signalprocessor 206 may utilize the peak signals 304 in determining thenecessary signal orientation to use in determining the distance andlocation of the second object 108. That is, the circularly polarizedsignal 300 may be used initially to detect presence of the object and todetermine the necessary signal polarization to use in determining thedistance of the object from the mm-wave system 104.

FIG. 4 illustrates an example use of multi-polarization signals by amm-wave system as described in present implementations herein. Themulti-polarization signals may include a combination of the horizontaland vertical signal polarizations to generate a particular amount ofsignal polarization by the plurality of transmitters 200.

Referring to FIG. 3 above where the signal processor 206 may utilize thepeak signals 304 in determining the necessary signal orientation to usein determining the distance and location of the second object 108, thepolarization controller 204 may utilize and combine, for example, bothhorizontal and vertical signal polarization from the first transmitter200-2 and second transmitter 200-4, respectively, to generate, forexample, a 45 degree—signal orientation 400. In this example, thecombination of the horizontal and vertical signal polarization mayadjust the E plane directions of the radiated electromagnetic fields to45 degree—signal orientation, which includes the peak signals withhigher SNR and of higher signal magnitude as discussed in FIG. 3 above.In this example still, rather than using an alternate horizontal orvertical signal orientation or polarization as discussed in FIG. 2above, the mm-wave system 104 may be configured to use multi-signalpolarization to detect and determine location of thin and small objectsduring dense weather conditions.

At the object end, the second object 108 may receive the transmittedmm-wave radar signals 112-4 that includes the 45 degree—signalorientation and thereafter, reflects a reflection signal 402, which mayinclude reflected signals that have consistent high signal magnitudeswith higher SNR.

FIG. 5 shows an example process chart 500 illustrating an example methodfor detecting slim objects by a mm-wave system as described herein. Theorder in which the method is described is not intended to be construedas a limitation, and any number of the described method blocks can becombined in any order to implement the method, or alternate method.Additionally, individual blocks may be deleted from the method withoutdeparting from the spirit and scope of the subject matter describedherein. Furthermore, the method may be implemented in any suitablehardware, software, firmware, or a combination thereof, withoutdeparting from the scope of the invention.

At block 502, transmitting a mm-wave radar signal by a plurality oftransmitters to an object is performed. For example, the plurality oftransmitters 200 of the mm-wave system 104 transmit mm-wave radarsignals 112 to the direction of the object. In this example, the mm-waveradar signals 112 may include at least two signal orientations. That is,the at least two signal orientations may include a plurality ofalternating horizontally and vertical polarized mm-wave radar signals.In other cases, the at least two signal orientations may further includedifferent sequence-combinations of the horizontal and vertical signalpolarizations.

At block 504, receiving of a return—mm-wave radar signal from the objectby a plurality of receivers is performed. For example, the receivedreturn—mm-wave radar signal 114-2 may include signal reflectionscorresponding to each of the at least two signal orientations. That is,depending upon the configuration of the plurality of the transmittedmm-wave radar signals, the reflected signals of the return—mm-wave radarsignal 114-2 may correspond to the signal polarization of thetransmitted mm-wave radar signals 112-2.

At block 506, detecting and determining a location of the object by aprocessor is performed. The signal processor 206 may be configured toprocess the received horizontal polarization reflection signal 212 andthe vertical polarization reflection signal 214 of the receivedreturn—mm-wave radar signal 114-2. For example, the signal processor 206may determine which signal between the horizontal polarizationreflection signal 212 and the vertical polarization reflection signal214 may include a higher SNR. In this example, the signal polarizationwith the higher SNR (i.e., horizontal polarization reflection signal 212or the vertical polarization reflection signal 214) may be utilized bythe signal processor 206 to determine the location of the first object106. In this example still, the signal processor 206 may send controlsignals that may be received by the polarization controller 204 in orderto change the alternating signal polarization or orientation into asingle signal orientation

What is claimed is:
 1. A millimeter-wave (mm-wave) system comprising: aplurality of transmitters configured to transmit a millimeter wave(mm-wave) radar signal to an object, the transmitted mm-wave radarsignal includes at least two signal orientations; a plurality ofreceivers configured to receive a return—mm-wave radar signal from theobject, the received return—mm-wave radar signal includes signalreflections corresponding to each of the at least two signalorientations; a processor configured to detect and determine location ofthe object based on the received signal reflections.
 2. The mm-wavesystem of claim 1, wherein the at least two signal orientations includeat least one horizontal polarization and one vertical polarization thatare transmitted by separate transmitters.
 3. The mm-wave system of claim1 further comprising a polarization controller coupled to the pluralityof transmitters, the polarization controller is configured to choose atransmitter from the plurality of transmitters for transmitting themm-wave radar signals, wherein each transmitter is configured to includefixed signal polarization.
 4. The mm-wave system of claim 1 furthercomprising a polarization controller coupled to the plurality ofreceivers, the polarization controller is configured to choose areceiver from the plurality of receivers for receiving the signalreflections, wherein each receiver is configured to include fixed signalpolarization.
 5. The mm-wave system of claim 1, wherein the transmittedmm-wave radar signal includes a frequency range within W band, the Wband includes a range of 75-110 GHz.
 6. The mm-wave system of claim 1,wherein the plurality of receivers is configured to have differentsignal polarizations in receiving the signal reflections.
 7. The mm-wavesystem of claim 1, wherein the processor is configured to determine thesignal reflection with a highest signal to noise ratio (SNR), whereinthe processor uses the determined signal reflections in determining thelocation of the object.
 8. A method of radar detection comprising:transmitting a millimeter wave (mm-wave) radar signal by a plurality oftransmitters to an object, the transmitted mm-wave radar signal includesat least two signal orientations; receiving a return—mm-wave radarsignal from the object by a plurality of receivers, the receivedreturn—mm-wave radar signal includes signal reflections corresponding toeach of the at least two signal orientations; detecting and determininglocation of the object by a processor, the detecting and determining ofthe location is based on the received signal reflections.
 9. The methodof claim 8, wherein the transmitting includes transmission of ahorizontally polarized signal and a vertically polarized signal bydifferent transmitters of the plurality of transmitters.
 10. The methodof claim 8, wherein the transmitted mm-wave radar signal includes afrequency range within W band, the W band includes a range of 75-110GHz.
 11. The method of claim 8, wherein the receiving utilizes differentsignal polarizations in receiving the signal reflections.
 12. The methodof claim 8 further comprising: determining the signal reflection with ahighest signal to noise ratio (SNR) by a processor, wherein thedetermined signal reflection is used as a basis for determining thelocation of the object
 13. The method of claim 8, wherein thetransmitting includes choosing a transmitter from the plurality oftransmitters for transmitting the mm-wave radar signals, wherein eachtransmitter is configured to include fixed signal polarization.
 14. Themethod of claim 8, wherein the receiving includes choosing a receiverfrom the plurality of receivers for receiving the signal reflections,wherein each receiver is configured to include fixed signalpolarization.
 15. The method of claim 8, wherein the detecting includescomparing signal magnitudes of a horizontally polarized return—mm-waveradar signal from a vertically polarized return—mm-wave radar signal.16. A device comprising: a plurality of transmitters configured totransmit a horizontally polarized mm-wave radar signal and a verticallypolarized mm-wave radar signal transmitted mm-wave radar signal to anobject using different transmitters; a plurality of receivers configuredto receive a horizontal polarization reflection signal and a verticalpolarization reflection signal that correspond to the transmittedhorizontally polarized mm-wave radar signal and the vertically polarizedmm-wave radar signal, respectively; a processor configured to detect anddetermine location of the object based on the received horizontalpolarization reflection signal or the vertical polarization reflectionsignal.
 17. The device of claim 16 further comprising a polarizationcontroller coupled to the plurality of transmitters, the polarizationcontroller is configured choose a transmitter from the plurality oftransmitters for transmitting the mm-wave radar signals, wherein eachtransmitter is configured to include fixed signal polarization.
 18. Thedevice of claim 16 further comprising a polarization controller coupledto the plurality of receivers the polarization controller is configuredto choose a receiver from the plurality of receivers for receiving thesignal reflections, wherein each receiver is configured to include fixedsignal polarization.
 19. The device of claim 16, wherein the transmittedhorizontally polarized mm-wave radar signal and the vertically polarizedmm-wave radar signal include a frequency range of 76-81 GHz.
 20. Thedevice of claim 16, wherein the processor is configured to utilize thereceived horizontal polarization reflection signal or the verticalpolarization reflection signal with a highest signal to noise ratio(SNR) in determining the location of the object.